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This paper presents the effect of tilt angle on static and dynamic performance characteristics of two gas-lubricated noncircular journal bearing configurations, namely two and four lobe bearings. The linearized system approach using finite element method is used to obtain both steady state and dynamic characteristics. The results of the investigation show that tilt angle has a significant effect on static and stability characteristics. With an increase in tilt angle, power loss is decreased while stability margins are increased.

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In grinding operation, cutting fluid is utilized for lubrication, cooling, chip removal from contact zone and also cleaning of grinding wheel. Despite these advantages, grinding fluids make many economic and environmental issues. On the other hand, dry grinding generally leading to thermal damages and reduction of surface quality level. Minimum Quantity Lubrication (MQL) technique is a new approach to elimination or reduction of cutting fluids that improves grinding performance by efficient penetration to the cutting zone. In this paper, in order to investigate the effect of MQL on grinding of steels, raw and hardened High Speed Steel have been selected. Grinding performance such as tangential grinding force, friction coefficient, roughness and morphology of the ground surface and chip form in three states of dry, conventional fluid and MQL have been studied and compared. The results show that MQL technique in comparison with the others lead to improvement of surface quality and also reduction of tangential grinding force and friction coefficient in hardened steel, but in the case of raw steel despite of reduction of tangential grinding force and friction coefficient, the surface quality is worst.

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Due to the energy concerns, it is always desired to run the mechanical elements under optimized operating conditions. Many lubricated mechanical elements such as gears, rolling element bearings, cam and followers etc. usually operate under mixed-lubrication regime. In this regime, both the lubricant film as well as the asperities contribute in carrying the load. The life span of these elements is divided into two regimes: running-in and steady-state. In this research an efficient model has been presented to predict the variation in asperities height during running-in. The predicted results are verified with experimentally-obtained published data. A parametric study on the effect of operating conditions such as load and speed as well as initial surface roughness and material hardness on the roughness variation during running-in has been conducted.

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Using of minimum quantity of lubricant in near dry machining is one the new method in machining processes that causes improvement of process. In this study, the role of near dry lubrication is investigated on tool wear in turning of Monel K500. The used tools are consisted of simple and viper ceramic tools. After preparation of process on lathe machine, the designed experiments are done. During the experiments force, surface roughness and tool wear are measured. The obtained results confirm that near dry lubrication causes the reduction of tool wear considerably. Also, viper ceramic tool has less tool wear rather than simple ceramic tool.

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Gears are one of the most important elements of any power transmission system. Among all types of gears, helical gears are more common due to their high capacity in power transmission as well as lower level of noise. The aim of this study is to present a model for analyzing the contact of teeth of helical gears considering thermal effects and surface roughness. In the present model, each helical gear is divided to several narrow spur gears in which each of the spur gears have a small rotation angle relative to the previous one. Also each contact point of gears is replaced with contact of two equivalent cylinders. Considering the fact that the governing regime for gears lubrication is the mixed-elastohydrodynamic regime, the total load is carried by lubricant and asperities' contact. Meshing and lubrication analysis of a pair of helical gears is conducted based on the load-sharing concept and parameters such as film thickness, friction coefficient and temperature rise are predicted. The predictions based on the load-sharing concept are compared to other published results Acceptable accuracy, short execution time along with considering thermal and roughness effects are some of the major characteristics of this study.

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In this paper, in order to avoid the problems induced by cutting liquids like higher cost, environmental pollution and dangerous for operator health in milling process and also using the benefits of them such as increasing tool life and machined surface quality, machining by minimum quantity of lubrication (MQL) or near dry lubrication was introduced and that’s effects on main outputs (consumed power and surface roughness) was compared with other lubrication methods such as lubrication by cutting fluids and by air. In order to perform a series of experiments and investigate the effects of different process parameters such as tools rotational speed, feed rate, gas pressure and liquid flow rate on main outputs, the Taguchi method of design of experiments was employed and then the analysis of variance (ANOVA) was used to find the most important factors effecting main outputs. The results obtained by experiments showed that employing near dry lubrication leads to lower electrical power and comparable surface roughness as compared with other lubrication methods. The analysis of variance showed that feed rate is the most important factor affecting consumed power and liquid flow rate is the most important factor influencing surface roughness.

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The productivity of a part is assessed based on factors such as dimensional and geometrical tolerances. In fact, tolerance features are the most important factors in shop drawing of an industrial part. The aim of present study is to empirically investigate the precision of holes created by helical milling method on AISI 4340 alloyed steel. This method refers to create the hole using milling tool, which moves along a helical path. By using helical milling, a high quality hole has been produced and there is no need for boring. Taguchi design of experiment was used to study the effects of process parameters including; cutting speed, feed rate, axial depth of cut and workpiece hardness on dimensional and geometrical tolerances of created hole. In addition, effect of minimum quantity lubrication method with two different oils and dry milling methods was studied. Results showed that the helical milling can be a suitable replacement for conventional drilling. In addition, cutting speed as the main parameter had significant effect on quality improvement of the created hole. On the other hand, in the helical milling, minimum quantity lubrication method using vegetable-based oil showed the best performance compared to mineral oil or dry cutting.

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High-speed milling of titanium alloys is widely used in aerospace industries for its high efficiency and good quality of product. The paper empirically studies surface roughness, topography and microhardness variations in high speed milling of Ti6Al4V alloy. The experiments were conducted under minimum quantity lubrication environment. Carbide end mill tool with TiAlN coating and 6 millimeter diameter was used. Full factorial method was used to design of experiments and analyze the effect of machining parameters including cutting speed and feed rate on surface roughness, topography and microhardness. The other cutting parameters i.e. axial depth of cut and radial depth of cut were constant. The results showed that a high quality surface with roughness of 0.2 µm can be obtained by using high speed machining method. Also, microhardness variations versus cutting speed has two-fold nature. It indicates that firstly, by increasing cutting speed up to 375 m/min, microhardness increases and after that, it declines remarkably. In addition, by increasing feed rate, surface microhardness rises and the maximum microhardness was obtained in cutting speed of 375 m/min and feed rate of 0.08 mm/tooth, which showed 57% increase in regard with hardness of the base material. The Images of surface topography showed that increasing of the cutting speed has a significant effect on reduction of surface tears and smears.

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Consumption of cutting fluids imposes high costs on industry. These cutting fluids contaminate the environment and are harmful to human health. Minimum quantity lubrication technique (MQL) is a new approach to reduction of cutting fluids consumption, improving efficiency of cutting fluid at machining zone and using harmless fluids. However, this technique faces cooling limitation in grinding. The purpose of this study is an accurate study of heat transfer mechanism in minimum quantity lubrication technique by its temperature numerical simulation and improving the cooling ability of its air jet by using a simple and inexpensive vortex tube. For this purpose, a system was designed and manufactured to measure the convection heat transfer coefficient of different conditions of MQL environments. The result of convection heat transfer tests shows 95% share of compressed air in heat transfer and also air pressure is a more important factor than temperature in cooling process. The result of temperature numerical simulation shows that by increasing pressure, the increasing rate of convection heat transfer coefficient decreases; also, the cooling ability temperature of the vortex tube at low thermal power is tangible. In grinding of soft steel, the minimum quantity lubrication technique with cold air (CAMQL) in comparison with other methods lead to significant reduction of tangential grinding force and friction coefficient, but in general, except in the case of optimum condition which has the highest heat transfer coefficient, surface finish is worse which relate to low heat transfer coefficient of gases at low pressures.

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Poor lubrication is known as an important factor in the bearings failure. Therefore, it is very important to detect the lubrication condition. Hydrodynamic lubrication, mixed lubrication and boundary lubrication are the basic regimes of the fluid film lubrication. In a proper condition, development of hydrodynamic pressure is adequate to support the load and the bearings operate under hydrodynamic lubrication condition. However, in most situations, they operate in mixed lubrication or boundary lubrication regime and have metal-to-metal contact. To establish these regimes, using the so-called Stribeck curve is a useful method. In this curve, the oil film thickness is proportional to the lubricant viscosity and sliding velocity and inversely proportional to the applied load. However, distinguish of the exact range of hydrodynamic lubrication regime from mixed and boundary regime using this curve and relation related to the sliding bearings, due to high number of affecting design factors and operating parameters is difficult. The present study focused on the acoustic emission measuring method in order to monitoring the lubrication conditions in a type of journal bearings. Thus, condition monitoring of the journal bearing lubrication is provided and the numerical value of operating variables of the bearing for lubrication regime change from hydrodynamic to mixed is achieved. Using wavelet method, frequency features for each regime is identified. Then, for each lubrication regime, metal-to-metal contact detection is performed.

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Super alloys due to special features such as high resistance to corrosion and heat, have the ability to maintain mechanical and chemical properties at extremely high temperatures which used in various industries, especially in the aerospace industry. On the other hand, very low heat transfer coefficient, high toughness with work hardening in these alloys caused the machining of them is seriously challenged. In the present study, the effect of cutting parameters on surface roughness of A286 superalloy has been studied in different lubrication conditions. Response surface method experimental design was used to plan experiments. In order to investigate the effects of machining parameters and conditions of lubrication on the surface roughness, Two factors - cutting speed and feed rate- on three levels and minimum quantity lubrication conditions and wet method are considered as the main parameters too. In order to investigate the Tool wear and workpiece surface quality, the images of Scanning Electron Microscope and optical microscope are used. The results show that using of the minimum quantity method of lubricant is caused to increase cooling-lubrication fluid particles penetrating power to the cutting zone and improves the process by reducing the surface roughness. It was observed that with increasing feed rate in fixed cutting speed, numerical values of surface roughness in Ra criterion are taken apart for different lubrication circumstances and its value for the minimum quantity method of lubricant is less, which shows the superiority of this method over the wet method.

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One of the new lubrication methods in machining processes is Minimum Quantity Lubrication (MQL). In this method, a very small amount of fluid by compressed air creates a spray and is used as lubricant. One of the advantages of this method compared to conventional (wet) lubrication is the reduction of environmental pollution and undesired effects on operator health. In the present study, the effect of minimum quantity lubrication on surface roughness in hard turning of 100Cr6 bearing steel has been investigated and compared with dry and wet machining methods. To perform MQL, some equipment have been added to the lathe machine. The tool used for material removal of 100cr6 steel is Nano-CBN that is a new generation of CBN tools with Nano technology. All experimental tests performed in dry, wet and MQL conditions. For investigation of surface roughness, each of cutting parameters include cutting speed, feed rate and cutting depth were selected in three different levels and all possible combinations of these parameters has been tested. According to experimental results and analysis of variance, feed rate 68%, lubrication method 14%, cutting speed 4% and cutting depth less than 1% affected on the surface roughness. The obtained results showed that the surface roughness in MQL method has been averagely decreased 42% and 30% in comparison with dry and wet machining, respectively.

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Minimum quantity lubrication (=MQL) technique has many technological and economic advantages in grinding operation. It not only improves general grinding performance such as surface integrity, grinding forces and wheel wear but also, it is eco-friendly technique because of its small consumption of cutting fluid. Despite these advantages, MQL technique has a serious thermal problem in grinding operations due to small amount of cooling. To overcome this problem combination of hybrid nanofluid and ultrasonic vibration has been suggested. Nanofluid can increase heat transfer from workpiece/wheel interface due to its high thermal conductivity. Also ultrasonic machining can decrease heat generation due to its reciprocating mechanism and reduction of time and length of contact between grain and workpiece. In this research hybrid Multi Walled Carbon Nano Tubes (=MWCNT) (with high thermal conductivity) and Al2O3 (with good lubrication effect) nanofluid has been utilized. The results have been shown that combination of MQL and UAG leads to decreasing of maximum grinding temperature up to 60.2% in comparison to dry grinding (from 254ºC to 101ºC). Moreover, friction coefficient and tangential grinding force have been reduced up to 35.9 and 69.2 percent respectively. Furthermore, any burning has not been observed with combinations of these techniques while severe burning has been observed in dry grinding. Surface morphology analysis has been shown decrease of plastic deformation and side flow. And finally the generated chips have been shown similarity of cutting mechanism in in the utilized techniques and conventional cutting fluids.

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Machining processes are the most important method to production in the industry. In these processes, the friction in tool-chip surface during the machining is one of the affecting factors on surface quality of work piece. The generated heat by friction, augment the tool wear mechanism and increase the wear rate of cutting edge which leads to reduction the surface quality. The high talent of aluminum to built-up edge formation during machining has the undesirable effect on the surface quality. In the present study in order to improvement the cooling-lubrication conditions in machining of 6061 aluminum alloy, a new cutting tool with creating micro-grooves on its rake face was developed to achieve the improving of cutting fluid transfer to machining zone and reducing the friction between tool-chip surface. Two types of micro-grooves have been created by laser machining process. Specimens by changing the machining parameters and types of the applying of cutting fluid to machining zone were machined. The experimental results obtained from surface roughness survey and prepared images of work piece surface by scanning electron microscope (SEM) and optical microscope showed that by creating the micro-grooves, the delivery conditions of cutting fluid to machining zone has improved and its effect to reduction of surface roughness is clearly visible. By comparison the results of two micro-grooves showed that direction of grooves is the most important parameters in its design, so that the perpendicular texture is not only improves the surface quality but also increase the surface roughness compared to non-texture tool.

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Ceramic matrix composites (CMCs) are a new class of high technology materials which can be utilized as a replacement for metallic super-alloys. CMCs have a vast array of applications in modern industries due to their upstanding properties, including low density, relatively high hardness and fracture toughness, and high corrosion and wear resistance. Extremely high hardness and inhomogeneous structure of CMCs cause unstable process and high grinding forces and temperature. This research was conducted in order to overcome the grinding challenges of these composites by recognizing and analyzing the effects of main process parameters comprising cutting speed, feed speed, and depth of cut on the grinding forces, specific energy, and grinding force ratio in three different environments including dry, wet and MQL grinding. To evaluate the significance of input parameters and their influence on the responses and also to derive predicting equations, Analysis of Variance (ANOVA) was employed. It was concluded that MQL technique is the most efficient cooling-lubrication method where implementation of this process reduces the tangential grinding force by 38.88% and normal grinding force by 31.16%, relative to dry grinding; however, the amount of force reduction in wet grinding is 34.22% for tangential grinding force and 24.81% for normal grinding force, relative to dry grinding. In addition, increase of cutting speed leads to reduced grinding forces and force ratio and higher amounts of specific energy, and also increase of feed speed and depth of cut cause higher grinding forces and force ratio and lower amounts of specific energy.

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Advanced ceramics are a group of materials that have been used in many industries due to their properties such as high temperature stability, high strength, high abrasion resistance and high corrosion resistance. Grinding process is one of the most important and most commonly used techniques for machining and polishing of ceramics. However, poor grindability, high surface defects in the workpiece due to the brittleness of ceramics and the high grinding forces, high wear rate of diamond wheel (tool), high costs due to the use of cutting fluid, low cutting productivity (low production rate), are of the problems of ceramics grinding. The minimum quantity lubrication (MQL) new technique is one of the methods recently introduced in machining processes aimed at improving lubrication performance of cutting fluids, reducing fluid consumption and promoting the use of low-hazard and environmentally friendly fluids. In this study, the minimum quantity lubrication technique was used in the grinding process of zirconia ceramic in order to investigate its effects on the grindability of ceramics. Also, since the type of lubricant and grinding wheel can affect the performance of minimum quantity lubrication in this process, the type of lubricant and diamond wheel were used as variables in the experiments. The grinding forces, surface roughness and surface texture of the grinded samples have been evaluated. The results show that under the minimum quantity lubrication conditions, applying the appropriate type of lubricant and grinding wheel can significantly affect the grindability of zirconia ceramic.

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Edible oils are exposed to physicochemical changes during heating, cooking and frying. Due to the high importance of this issue and the public perception of the health of oils prepared in oil shops in the city, this study was conducted to evaluate and compare the thermal stability of sesame oils prepared by shop and industrial press. Sesame oil samples were prepared from four lubrication centers in Ahvaz and their stability during 12 days during the thermal process with tests, acid number, peroxide, anisidine, Totex and iodine to evaluate the oxidative stability and also measure the composition of fatty acids with The use of gas chromatography was performed and evaluated according to Iranian national standards. The results showed that linoleic acid (C18: 2) Level (41.5-42.7) Percentand and oleic acid (C18: 1) Level (38.5- 39.47) Percentand of the maximum fatty acids in sesame oils were studied which The fatty acids of all samples were in the range specified by the National Standard of Iran. The results of acid, iodine, peroxide, anisidine and totex tests all showed a significant difference between the sample of industrially prepared sesame oil and other oils prepared by shop press method and the better performance of industrial oil at a significant level Showed 5%. By interpreting the data and results, it can be found that sesame oils prepared by industrial method have higher thermal stability than oils prepared by shop press method and are more suitable for thermal applications.

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In this study, an example of the results obtained from the combination of the vibration monitoring program and the root cause analysis approach for the electromotor roller element bearings of the cement factory’s mill fan has been presented and examined. By registering the inspectors' reports on the release of abnormal sound from the bearings, the vibration data recorded in the monitoring program were equipped and, by carefully checking the vibration trends of the machine, sensible increase in the bearing condition index (BC) have seen. By matching the fault frequency with the frequency elements of the roller bearing, predicted is failure in the bearing' cage, which will be verified by visited and reviewed. The detect of the root cause of the failure is on the agenda for this purpose, paid investigated the causes of failure in the bearings and due to the inspection history, finally specified the use of the bearing is not suitable due to the velocity factor, as well as the factors of the lubrication interval and the amount of lubrication charged can be explained by the reasons for failure in the machine.

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In internal combustion engines, due to cyclic loading and wear between the upper surface of the piston ring and the upper groove of the piston, the fretting fatigue phenomenon could occur. In this research, the effect of lubrication and the heat treatment on the fretting fatigue behavior of aluminum-matrix nano-composite have been investigated. The fretting fatigue test was performed in fully-reversed loading condition and at the room temperature. In addition, the S-N curve and fretting fatigue properties of piston alloys were obtained. The microstructure and the fracture surface were examined by the optical and microscopy and the field emission scanning electron microscopy. The results showed that the failure behavior was brittle. In addition, the lubrication and the heat treatment improved the fretting fatigue lifetime of the piston alloy.